n] EXTERNAL STRUCTURE OF A FLEA 35 



and Taschenberg. Modern opinion is all but un- 

 animous on this point. 



There remains, however, a second question. Even 

 if it be agreed that there must be a distinct order 

 for Suctoria, Aphaniptera, Siphonaptera, or fleas ; 

 where ought that order to be placed? In which 

 other order of insects must we look for the nearest 

 relations of fleas ? For a time after the acceptance 

 of the fact that insect forms have been evolved, and 

 not separately created, the ancestors of fleas were 

 searched for among some species of fly. 



Then Kraepelin rejected the view that flies were 

 as closely related to fleas as most entomologists 

 thought and his followers could only find points of 

 difference and no points of resemblance. Dahl (1899), 

 a German, then took up the cudgels for the fly 

 theory. Dahl pointed out the resemblance between 

 fleas and a group of flies called Phoridw also 

 parasitic on warm-blooded animals. During the 

 ensuing years the debate was resumed afresh 

 with much liveliness and sometimes with a little 

 acrimony. 



The fleas were placed by MacLeay and by 

 Balbiani between the Diptera and Hemiptera ; 

 by Leach between the Hemiptera and Lepidoptera ; 

 by Duges between the Hymenoptera and Diptera ; 

 by Brauer between the Diptera and Coleopt&ra* 

 Handlirsch thinks that fleas have no connection at 



32 



